ensurism

A validation and conditional assignment utility belt.

Install

npm install ensurism

Contents

• Use Cases
  • Validation
  • Environment Variables
  • Global Configuration
• Utils
  • assert
  • take
  • ensure
  • coerce
  • select
  • collect

Use Cases

Validation

The most general util for validation is ensure, wich uses JSON Schema to validate your data. However, be sure to take a look at the remaining utils to find the best fits for your use cases.

Environment Variables

import process from 'node:process';

import { collect, ensure } from 'ensurism';

// Will always be 'development', 'production', or 'test'
const NODE_ENV = ensure(process.env.NODE_ENV, {
  type: 'string',
  enum: ['development', 'production', 'test'],
  default: 'development'
});

// Collecting -mapping- properties
const env = collect(process.env, ({ get, assert, ensure, coerce }) => ({
  FOO_VAR: get(),
  BAR_VAR: assert(),
  APP_URI: ensure({ type: 'string', format: 'uri' }),
  APP_PORT: coerce('number'),
  NODE_ENV: ensure({
    type: 'string',
    enum: ['development', 'production', 'test'],
    default: 'development'
  })
}));

Global Configuration

You might want to create a configuration object that relies on certain values. In the example below, we collect environment variables, and later use select to conditionally set the properties bar and baz for our final configuration object.

import process from 'node:process';

import { into } from 'pipettes';
import { collect, select } from 'ensurism';

export const configuration = into(
  collect(process.env, ({ ensure }) => ({
    NODE_ENV: ensure({
      type: 'string',
      enum: ['development', 'production', 'test'],
      default: 'development'
    })
  })),
  ({ NODE_ENV }) => ({
    env: NODE_ENV,
    foo: 'foo',
    bar: select(NODE_ENV, {
      default: 1,
      production: 2,
      development: 3
    }),
    baz: select(NODE_ENV, {
      default: 1,
      production: 2,
      test: 4
    })
  })
);

Utils

assert

Throws if data is undefined.

• Signature: assert(data, options)
• Params:
  • data: the input data.
  • options: optional object with optional properties:
    • name: a name to be used for error messages.
    • message: an error message to use instead of the default.
    • deep: if true and data is an array or a record, assert will also throw if any of their elements are undefined.
• Returns: the input data.

import { assert } from 'ensurism';

// Succeed
assert('foo');
assert([undefined]);

// Fail
assert(undefined);
assert([undefined], { deep: true });

take

Returns the input data for records and basic types; for arrays, however, one of multiple strategies can be applied:

• Signature: take(data, options)
• Params:
  • data: the input data.
  • options: optional object with optional properties:
    • name: a name to be used for error messages.
    • assert: whether to assert the final output value is not undefined.
    • strategy: applies to data arrays; one of:
      • "first": it will return the first array item, if any. This is the default strategy.
      • "one": it will throw if the input array has more than one element, and return its first item, if any.
      • "maybe": it will return the first defined array item, if any.
• Returns: the input data if it is a record or a basic type; if data is an array, it will return a data array value as per the specified strategy.

import { take } from 'ensurism';

// Succeed
take(['foo'], { strategy: 'one' }); // 'foo'
take(['foo', 'bar'], { strategy: 'first' }); // 'foo'
take([undefined, 'foo'], { strategy: 'maybe' }); // 'foo'

// Fail
take(['foo', 'bar'], { strategy: 'one' });
take([undefined], { assert: true, strategy: 'first' });

ensure

Throws if data doesn't conform to a given schema. If the schema has default values, they will be assigned to the returned data. Additional properties, when allowed by the schemas, will not be removed. No mutation will occurr for input data.

Uses JSON Schema validation, as implemented by ajv. Further string format validation is provided by ajv-formats and ajv-formats-draft2019.

• Signature: ensure(data, schema, options)
• Params:
  • data: the input data.
  • schema: either a JSON Schema object with a type property, or a valid schema type, as a string.
  • options: optional object with optional properties:
    • name: a name to be used for error messages; if empty, schema.title will be used instead when available.
    • assert: whether to assert the final output value is not undefined.
• Returns: a clone of the input data with, if it applies, the default values assigned as specified by schema.

import { ensure } from 'ensurism';

// Succeed
ensure('foo', 'string'); // 'foo'
ensure(undefined, 'string'); // undefined
ensure(undefined, { type: 'string', default: 'foo' }, { assert: true }); // 'foo'

// Fail
ensure('foo', 'number');
ensure(undefined, 'string', { assert: true });

coerce

Coerces data to the root schema type, then validates the data against the schema by using ensure. Inner elements for objects and arrays will not be coerced.

• Signature: coerce(data, schema, options)
• Params:
  • data: the input data; undefined won't be coerced into the schema type.
  • schema: either a JSON Schema object with a type property, or a valid schema type, as a string.
  • options: optional object with optional properties:
    • name: a name to be used for error messages; if empty, schema.title will be used instead when available.
    • assert: whether to assert the final output value is not undefined.
• Returns: a clone of the input data with, if it applies, the default values assigned as specified by schema.

The coercion rules from each data input type are as follows:

• strings:
  • "string": returns the input string with quotes (") removed, if within quotes.
  • "number", "integer": fails if NaN.
  • "boolean": false for falsy value strings:
    • ""
    • "\"\""
    • "0"
    • "false"
    • "null"
    • "undefined"
    • "NaN"
  • "null": fails if not a falsy value string.
  • "array", "object": parses with JSON.parse; fails if not a JSON string.
• numbers:
  • "string": a number string.
  • "number", "integer": a number.
  • "boolean": false for 0, true otherwise.
  • "null": fails if not 0.
  • "array", "object": it will fail.
• boolean:
  • "string": "true" or "false".
  • "number", "integer": 0 for false; 1 for true.
  • "boolean": same as data source.
  • "null": fails if not false.
  • "array", "object": it will fail.
• null:
  • "string": "null".
  • "number", "integer": 0.
  • "boolean": false.
  • "null": null.
  • "array", "object": it will fail.
• array:
  • "string", "number", "integer", "boolean", "null": it will fail.
  • "array": same as data source.
  • "object": an object with index numbers as keys.
• object:
  • "string", "number", "integer", "boolean", "null": it will fail.
  • "array": an array of object values.
  • "object": same as data source.

import { coerce } from 'ensurism';

// These will succeed
coerce('foo', 'string'); // 'foo'
coerce('"foo"', 'string'); // 'foo'
coerce('0', 'number'); // 0
coerce('foo', 'boolean'); // true
coerce('null', 'boolean'); // false
coerce('false', 'null'); // null
coerce('{ "foo": "bar" }', 'object'); // { foo: 'bar' }
coerce(10, 'boolean'); // true
coerce(0, 'null'); // null


// These will fail
coerce('foo', 'number');
coerce('foo', 'null');
coerce('1, 2, 3', 'array');
coerce(1, 'null');

select

Given a value and a selector object, it will return the value of the selector's property matching that value. If selector doesn't have such property but it does have a default key, it will return its value instead.

If a strategy other than "fallback" is specified, the selected value -if any- will be merged with the default value -if any- following the specified strategy.

• Signature: select(data, selector, options)
• Params:
  • data: property to select from selector.
  • selector: and object of values.
  • options: optional object with optional properties:
    • name: a name to be used for error messages.
    • assert: whether to assert the final output value is not undefined.
    • strategy: applied when there's both a selector.default and data for value -see merge strategies; one of:
      • "fallback": returns the data for selector[value] if available, otherwise returns selector.default. This is the default strategy.
      • "shallow": produces a shallow merge clone of the data.
      • "merge": produces a deep merge clone of the data, excluding arrays.
      • "deep": produces a deep merge clone of the data, including arrays.

import { select } from 'ensurism';

// These will succeed
select('foo', { foo: 'bar', bar: 'baz' }); // 'bar'
select('foo', { default: 'bar', bar: 'baz' }); // 'bar'
select('foo', { default: { bar: 'bar' }, foo: { baz: 'baz' } }, { strategy: 'shallow' }); // { bar: 'bar', baz: 'baz' }

// These will fail
select('foo', { bar: 'baz' }, { assert: true });

collect

A conveniency function for when you want to use any of the previous utils for several keys in an object, and expect the response to contain similarly named properties.

• Signature:collect(data, collection, options)
• Params:
  • data: an object of values.
  • collector: a function, taking an object with methods get, assert, take, ensure, coerce, and select as an argument. These methods have the same signature as the similarly named functions but omitting their first data argument.
  • options: optional object with optional properties:
    • failEarly: boolean, whether to fail as soon as one of the values throw, otherwise compacting all errors in a single error. Default: false.
• Returns: an object as defined by collector.

import { collect } from 'ensurism';

const result = collect(
  {
    a: 'foo',
    b: 'bar',
    c: ['baz', 'foobar'],
    d: 'foobaz',
    e: 'barfoo',
    f: 'barbaz'
  },
  ({ get, assert, take, ensure, coerce, select }) => ({
    a: get(),
    b: assert(),
    c: take('first'),
    d: ensure('string'),
    e: coerce('boolean'),
    f: select({
      default: true,
      barbaz: false
    })
  })
);

// `result` would be an object such as:
({
  a: 'foo',
  b: 'bar',
  c: 'baz',
  d: 'foobaz',
  e: true,
  f: false
});